Observation window



July 10, 1962 G. J. NYBERG OBSERVATION WINDOW Filed Nov. 15, 1960 JNVENTOR.

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United States Patent() 3,043,250 OBSERVATRON WINDOW George J. Nyberg, Worcester, Mass, assignor to Riley Stoker Corporation, Worcester, Mass, a corporation of Massachusetts Filed Nov. 15, 1960, Ser. No. 69,476 3 Claims. ((31. 110-179) This invention relates to an observation window and more particularly to apparatus arranged for viewing the interior of the furnace of a steam generating unit.

In the manufacture of observation windows for the furnaces of steam generating units it has been common practice, particularly where a pressurized furnace is used, to provide for the introduction of pressure air flowing inwardly toward the furnace when the observation Window is open. This is to prevent the flow outwardly through the Window of hot products of combustion or, in some instances, of flame. Such a window requires a large amount of air at a substantial pressure and requires special apparatus for producing such high pressure air. Also, an interlock mechanism must be provided to assure that before the furnace door is opened the air flow has been established toward the furnace. As has been stated above, this is to prevent the observer from being burned when he places his face in front of the open window. Such an apparatus is, therefore, quite expensive to manufacture and to maintain. These and other difiiculties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide an observation window which is inexpensive to manufacture and which functions in an eifective manner.

Another object of this invention is the provision of an observation window for a pressurized furnace having a glass panel which panel is fully protected from damage due to the heat of the furnace.

A further object of the present invention is the provision of a glass observation window for a furnace having means for protecting the glass from damage when the observation window is not being used.

it is another object of the instant invention to provide an observation window for a pressurized furnace which is low in cost, simple in construction, and which requires very little maintenance.

It is a further object of the invention to provide an observation window for a pressurized furnace which requires no special air supply and in which no interlock is required to assure that a special air supply is turned on before the window is used. I

A still further object of this invention is the provision of an observation window which is free of gas leakage.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings in which:

FIG. 1 is a front elevation of an observation window embodying the principles of the present invention;

FIG. 2 is a sectional view of the invention taken on the line IIII of FIG. 1;

FIG. 3 is a vertical sectional view of the invention taken on the line III-4H of FIG. 1; and

FIG. 4 is a sectional view of a portion of the invention taken on the line IVIV.of FIG. 1.

Referring to the drawings, it can be seen that the observation window, indicated generally by the reference numeral 10, is shown in use with the wall 11 of a steam generating unit 12. The window is provided with a ice mounted in a bore 14 through the wall 11. The wall 11 generally tubular housing 13 which extends through and is is made up of a series of waterwall tubes 15, one tube 16 being bent laterally to form an access opening 17 through the wall aligned with the bore 14. The rear surfaces of the tubes 15 are covered with plastic refractory 20 embedded in screen 18. Sheet metal 19 overlies the refractory 2t) and is provided with a box-like structure 21 surrounding the housing .13. In order to bend the tube 16 sideways to form the opening 17 it is necessary to move another tube 22 rearwardly and laterally into the boxlike structure 21. Outside of the sheet metal 19 is arranged two layers of fiberglass mat 23 and 24 which are in turn covered with a weatherproof sheet 25 of fiberglass. The inside of the housing 13 is provided with a refractory sleeve 26. The inner end of the housing 13 is welded to the waterwall tubes at the points at which it contacts them.

The outer end of .the housing 14 is provided with a cover 27 which is normally bolted to the housing by means of cap screws 28. The cover is formed of cast iron and is provided with a central bore 29. Surrounding the bore on the exterior is a slight ridge 31 to which is attached a ring 32. A bore 33 is aligned with the bore '29 of the cover and is provided on its inner side with a slight counterbore 34 in which is locked a protective screen 35. The inner surface of the cover 27 is provided with another counterbore 38 concentric with the bore 29 and having located therein spring clips 39 the outer ends of which are screwed in the counterbore 38 and the inner ends of which press against the glass 37 and hold it in place in its counterbore 36. A resilient gasket lies between the glass 37 and the bottom shoulder of its counterbore 36. A similar gasket exists between the end of the housing 13 and the cover 27.

Extending inwardly of the housing 13 adjacent its outer end is an annular flange 41 on the outer surface of which is welded an aperture plate 42 having a circular aperture 43 approximately the same size as the bore 29 in the cover. Normally lying against the furnace side of the plate 42 is a door 44 formed of sheet metal and slightly larger in diameter than the aperture 43. The door 44 is formed with a number of .inch high protrusions 45 which actually contact the plate 42 around the edge of the aperture 43 and which define an annular opening between the plate and the door. Bolted to the upper portion of the door 44 are hinge blocks 46 having hinge pins or pintles 47 mounted in apertures in hinge blocks 48 bolted to the inner surface of the plate 42 at either side. The hinge blocks 46 and the hinge blocks 48 along with the pintles 47 constitute a hinge for the door 44. Welded to the outer'surface of the door 44 is an ear 49 to which is hingedly attached one end of a link 51, the other end of which is pivotally attached to one end of a bell crank 52. The other end of the bell crank 52 is pivoted to atransverse shaft 53 pivotally mounted in the housing 13 in a manner best shown in FIG. 4. The housing 13 is provided with a boss 54 having a bore 55 in which the shaft 53 is rotatably carried. The boss is provided with a threaded counterbore 56 in which is mounted a packing sleeve 57. Between the inner end of the packing sleeve and the bottom of the counterbore is located a packing 58 which, when compressed by the sleeve 57, presses radially inwardly against the shaft 53 and prevents any gas leakage. Bolted to the exterior of the housing 13 is a handle box 59 into which the outer end of the shaft 53 extends. The outer end of the shaft is provided with a handle 61. A block 62 is fastened to theouter end of the shaft adjacent the handle and is provided with two stop arms arranged at an angle somewhat less than A slight abutment 63 is formed "on the inner surface of the box 59 for contact with these limit arms as the handle 61 is moved. Between the block 62 and the sleeve 57 is mounted a torsion spring 64 whose ends are attached to the block 62 and to the sleeve 57 in such-a manner that the shaft 53 is normally s pring-biased to keepthe door 44 in closed position against the plate 42. i

through the furnace wall. This pressure, generally speaking, is a static gas pressure and makesitself felt on the interior of the housing 13. However, the bottom of the I 'movement from a first normal position covering the aperture to a second observation position away from the exterior of the housing'33 is connected through an opening 65 and pipes 66 to the forced draft duct near the outlet of the forced draft fan (not shown). This provides a source of air under pressure connected to the outer end of the housing 13 adjacent the inside of the window pane 37. This pressure is slightly greater than the furnace pressure and, therefore, air flows through the aperture 43 and theplate 42 through the small annular space between the door 44 and the plate 42 which exists because of the .protuberances 45 which keep the door and plate slightly separated even when the door is closed. This slight-flow of air which passes outwardly throughthe opening 17 in the furnace tends to keep the observation window clear of dust and gases at all times. V

Also, the air flowing in this manner prevents the furnace 'gases' from entering the observation window and dirtying the glass; The glass, of course, is free of possible damage through radiation' from the furnace because the door 44 interferes at all times exceptwhen observation is actually being made. When the operator wishes to look into the furnace he grasps the handle 61 and holds it downwardly. This rotates the shaft 53 against'the torsional resistance of the spring 64 which tends to keep it up in the other difeet-ion. The handle is rotated downwardly until the limit arm of the'block 62 strikes the underside of the abutment 63Vand'thenthe shaft can be rotated no longer. When it has beenrotated this far, the shaft acting through the crank arm'52 and the link 51 has moved the door 44 about 7 its hinge axis to the position shown in dotted lines in FIG. 3. When it is in this position, the lower limit arm of the block 62 has come against the bottom of the abutment 63. The operator then peers through the screen 35 and the glass 37 through the opening 17 into the furnace. Release of the handle 61 permits the spring 64 to take over and bring the door back down to its original position.

i It will be seen that the observation window of the invention is absolutelyv gastight; the only moving part being through thebore 55 and the shaft 53 which is provided with an adequate packing 58. There is no danger of the door 44 being left in its raised position so that the glass is subjected to furnace heat. At all times the air sweeping through the window and out through the opening 17 keeps the instrument clean and free of dust. There is no special compressor and tank required for supplying air to the observation since it uses a small amount of forced draft This air, in addition to keeping the interior of the observation Window clean, alsocools the parts. Generally speaking, the air required would be about 25 cubic feet per minute at 4 inches ofwater gauge differential between the air connection at the opening 65 and the interiorof the furnace.

' It is obvious thatminor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, de-

The invention having been thus described, What is claimed as new and desired to secure by Letters Patent is: l

1. An observation window for a furnace wall, compris 7 ing an'elongated tubular housing adapted to be mounted within an opening through the wall, a'cover with a' glass pane fastened to the outer end of the housing, a plate with an'aperture extending across the housing intermediate of aperture, a handle located exterior of the housing and extending into the housing for moving the door-from one position to theother, means connecting the housing to the forced draft air source of the furnace for receiving air at slightly greater pressure than the furnace tocause a continuous flow of "air from the housing into the furnace, a spring biasing the handle to a position such'that the door is in the first position, and protuberances extending between the door and theplate to prevent the door from completely closing the aperture so that a continuous leakage of air takes place around the door and into the furnace even when it is in the said first position.

2. An observation window for a furnace wall, comprising (a) an elongated tubular housing. adapted to be mounted within an opening through the wall, (b) a cover with a glass pane fastened to the outer end of the housing, 7 (c) a plate with an aperture extending across the housing intermediate of its ends, (d) the door hingedly mounted in the housing for movement from a first normal position covering the aperture to a second observation position away from the aperture,

(e) a handle located exterior of the housing and extending into the housing formoving the door from one position to the other, 7

(f) means connecting the housing to the forced draft air source of the furnace for receiving air at slightly greater pressure than the furnace to cause a continuous flow of air from the housing into the furnace. I

(g) a spring biasing the handle to a position such that the door is in the first position,

(h) and means extending between the door and the plate to prevent the door from completely closing the aperture so that a continuous leakage of air takes place around the door and'into the furnace even when it is in the said first position. 1 I

3. .An observation window for a furnace wall, compris ing (a) an elongated tubular housing adapted to be mounted within an opening through the wall,

(b) a cover with a glass pane fastened to the outer end of the housing, 7

(c) a plate with an aperture extending across the housing intermediate of itsends,

*(d) a .door hingedly mounted in the housing for movement about an axis at a right angle to the axis; of the tubular housing, the door being movable from a first normal position covering the aperture to a sec- 0nd observation position away from the aperture, (e) a handle located exteriorly of the housing and extending into the housing for moving the door from one position to the other, 7 V v (f) a seal extending between the handle and the housing at the point of emergence of the handle from the housing, 7 i

(g) means connecting the housing to the forced draft source of the furnace for receiving air at slightly greater pressure than the furnace to cause a continuous flow-of air from the housing into the furnace,

(h) a spring biasing the handle through a position such that the door is in the first position, V

(i) and protuberances extending between the door and the plate to prevent the door from completely closing the aperture so that a continuous leakage of air takes place around the door and into the furnace even whenit is in the saidfirst position.

References Cited in the file of this patent UNITED STATES PATENTS 1,717,637 ,Vastine Iune'18,1929.

'Ligon Mar. 1, 1960 

